Amoeboid Swimming: A Generic Self-Propulsion of Cells in Fluids by Means of Membrane Deformations

Alexander Farutin (1) , Salima Rafaï (1) , Dag Kristian Dysthe (2) , Alain Duperray (3) , Philippe Peyla (1) , Chaouqi Misbah (1)

1 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
2 PGP - Physics of Geological Processes [Oslo]
3 INSERM U823 - Institut d'oncologie/développement Albert Bonniot de Grenoble

Microorganisms, such as bacteria, algae, or spermatozoa, are able to propel themselves forward thanks to flagella or cilia activity. By contrast, other organisms employ pronounced changes of the membrane shape to achieve propulsion, a prototypical example being the Eutreptiella gymnastica. Cells of the immune system as well as dictyostelium amoebae, traditionally believed to crawl on a substratum, can also swim in a similar way. We develop a model for these organisms: the swimmer is mimicked by a closed incompressible membrane with force density distribution (with zero total force and torque). It is shown that fast propulsion can be achieved with adequate shape adaptations. This swimming is found to consist of an entangled pusher-puller state. The auto-propulsion distance over one cycle is a universal linear function of a simple geometrical dimensionless quantity $A/V^{2/3}$ (V and A are cell volume and its membrane area). This study captures the peculiar motion of Eutreptiella gymnastica with simple force distribution.

Mots clés: microswimmers; active swimming

Domaines: Biophysique [physics.bio-ph]

Alexander Farutin, Salima Rafaï, Dag Kristian Dysthe, Alain Duperray, Philippe Peyla, et al.. Amoeboid Swimming: A Generic Self-Propulsion of Cells in Fluids by Means of Membrane Deformations. Physical Review Letters, 2013, 111 (22), pp.228102. ⟨10.1103/PhysRevLett.111.228102⟩. ⟨hal-00908796⟩